DE102010020078A1 - Sealing screw with shortened cone section - Google Patents

Abstract

The present invention is in the field of screws and in particular threaded screws. In many cases it is desirable to use a screw to seal the hole into which it is inserted in a liquid-tight or gas-tight manner. There are various proposals in the prior art for this, including a screw that can create the seal without a washer made of flexible, soft material. This screw is published in the patent specification DE 103 14 948. In order to get a screw of this type also usable for chamfered holes, a steep tapered section (12) is proposed (16) and the thread, preferably directly adjacent to the screw head (16) ), and has a transition section (14) which runs flatter in relation to this and to the shaft which extends further cylindrically.

Description

Field of the invention

The present invention is in the field of screws and more particularly threaded screws.

State of the art

Screws are widely known. They are used for fastening and clamping together two (or more) workpieces, one having a through hole and the other a hole with a counter thread, or also for closing openings, as in the case of an oil drain plug.

The tightening of a screw connection causes the application of an axial normal force due to low elastic deformation of the shank and the workpiece. The screw shaft is thereby stretched in the elastic region, the stressed workpieces in the bore area compressed. The connection itself is thus non-positive and has properties of a spring.

In many cases, it is desirable to seal the hole in which it is inserted, liquid-tight or gas-tight with a screw. For this purpose, there are various proposals in the prior art, including a screw that can create the seal without interposed shim made of flexible soft material. This screw is published in the patent DE 103 14 948 ,

This screw fulfills both tasks placed on it for many applications, especially in castings with rough and uneven surface bearing surfaces for the screw head, as they are typical for castings in the automotive industry, such as gearboxes, crankshaft housings and motor housings, namely the stable and secure connection the components despite their vibration, and their thermally induced expansion and shrinkage processes, and also the seal of the through hole.

However, the screw can only be used conditionally. If the hole in which the screw is inserted has a chamfer, the requirements with regard to the stability of the screw connection can not always be maintained, for example at chamfer angles of approximately 45 ° and larger, relative to the hole axis.

The object of the present invention is to further develop the aforementioned screw or to provide an alternative with which it can also be used for chamfered holes.

Advantages of the invention

The objective solution is achieved by a screw according to device-related main claim. The procedural solution is achieved by the doctrine of the procedural subsidiary claim. From the respective subclaims, further advantageous features.

According to an essential aspect of the invention, there is disclosed a threaded screw comprising a shaft provided with a thread suitable for screwing into a mating thread and a screw head adapted to rest over a chamfered hole, characterized in that the shaft between the screw head and the thread, preferably directly adjoining the screw head, has a steeply extending cone section, and has a shallower transition section relative to this - to the extent laterally cylindrical - shaft.

When screwing the screw, the cone portion is first pressed against the transition region of the chamfer to the cylindrical hole portion, this deformed thereby forming a sealing surface between the cone portion of the screw and the transition area at the hole, and wherein the screw head during further screwing the screw in contrast to the described State of the art reproducibly comes to rest and on further screwing the screw head exerts a force on its support surface which is large enough to produce a sufficiently large voltage between the components, or between the screw and the component, and loosening the screw by vibration , or to prevent thermally induced expansion and shrinkage movements reliably.

Angles are always given herein in relation to the vertical, be it hole axis or screw axis.

It is advantageous if the angle Alfa of the steeply tapering cone section to the screw axis is in the range of 5 ° to (Beta minus 2 °), and Beta is the angle of the chamfer to the hole axis, with a cone length in the range of 1.0 mm to 2 , 0 mm, and a difference between hole diameter and screw diameter of about 0.6 mm.

It is even more advantageous if the range for Alfa is from 25 ° to 40 °, more preferably from 30 ° to 38 °, and even more preferably from 32 ° to 36 °.

For all the above-mentioned angle ranges, the cone length must nevertheless be so long that they are compatible with the chamfer surface and preferably with the said transition region to the cylindrical remainder of the through hole comes in contact and deformed during further screwing this purpose of forming the sealing surface. It is assumed that the material of the screw is harder than that of the component or the contact surface, if the component should not be constructed of a homogeneous material. The conical surface must not be too long, the conical section with its maximum diameter should not be too large and the clearance between the screw and through hole should not be too low, otherwise you will not be able to screw in the screw so far that the screw head rest against its provided bearing surface passes and produce the required depending on the application voltage between the components and between the screw head and adjacent component reproducible. The examples below give the framework within which this is generally achievable.

If an annular circumferential groove is provided between the screw head and the steep cone section, then the hole edge is thereby deformed when the screw is tightened, thereby producing the required tightness, and a bead forming laterally and upwardly in accordance with the deformation finds space in the interior of the groove. The screw can then still be tightened with the screw head according to the specific requirements of the particular application, whereby the voltage to be achieved between the screw head and the bearing surface can be realized. Thus, the screw can be used at least in some cases, even if a hole once has no bevel or only an insufficiently pronounced chamfer.

• a) Einstecken einer Schraube nach Anspruch 1 in das Durchgangsloch,
• b) Eindrehen der Schraube in das Gegengewinde, wobei zunächst nur der Konusabschnitt gegen den Übergangsbereich der Fase zum zylindrischen Lochabschnitt gedrückt wird, dieser dadurch verformt wird, wodurch sich eine Dichtfläche zwischen Konusabschnitt der Schraube und Übergangsbereich am Loch ausbildet,
• c) weiteres Eindrehen der Schraube solange bis der Schraubenkopf eine Kraft auf seine Auflagefläche ausübt, die groß genug ist, um Losdrehen der Schraube durch Vibration, oder thermisch bedingte Ausdehnungs- und Schrumpfbewegungen zu verhindern, bzw. bis die notwendige Spannung zwischen den Bauteilen oder zwischen Schraubenkopf und angrenzendem Bauteil geschaffen ist.

According to an essential method aspect of the invention, a method is disclosed for producing a screw connection between at least two components, wherein the one component has a beveled (chamfer) through-hole for the screw shank, and the through-hole is to be sealed with the screw head, characterized by the steps:

• a) inserting a screw according to claim 1 in the through hole,
• b) screwing the screw into the mating thread, wherein at first only the cone section is pressed against the transition region of the chamfer to the cylindrical hole section, this is deformed thereby forming a sealing surface between the cone section of the screw and the transition zone at the hole,
• c) further screwing the screw until the screw head exerts a force on its bearing surface, which is large enough to prevent loosening of the screw by vibration, or thermally induced expansion and shrinkage movements, or until the necessary voltage between the components or between Screw head and adjacent component is created.

The screw according to the invention can be used particularly advantageously for the connection of components of housings which have a liquid or a pressurized gas inside, and whose tightness must be maintained by other measures such as elaborate immersion baths, such as gearboxes, crankshaft housings and motor housings. In particular, there are almost exclusively leaks in the area of the blind holes and the through holes, which in turn are caused by cracks which form after casting of the component due to the cooling of the material.

The screw according to the invention can be used for all screw sizes and matching through hole sizes.

Brief description of the figures

1 shows in an enlarged schematic partial view left and top a screw according to the invention with a steeper cone portion and flatter cone portion, and in parts the screw head and the screw shaft and right and down to the right side hole edge of the through hole of a component, wherein the cone portion of the screw and the transition region between bevel and adjacent cylindrically extending hole still have no contact.

2 is a representation according to 1 , where the screw has already approximated the expected contact point by screwing in, but still no contact has occurred,

3 is a representation according to 1 and 2 wherein the screw with its cone section has deformed the transition region of the chamfer to the cylindrical part of the hole in a small deformation section, but the screw head itself still has no contact with its bearing surface,

4 is a representation according to 1 . 2 and 3 , wherein the screw head has now been tightened with its target torque, and the deformation portion has become even larger, and wherein the required voltage between the screw head and its bearing surface and the voltage between the component with the through hole and the second component to be connected with the mating thread achieved is.

EXAMPLES

The material of the components is a common aluminum alloy, or an alloy predominantly of aluminum and magnesium, as usual in gearboxes, crankshaft housings or engine housings. The screw was designed as a standard steel screw for this application and as a DIN M8 size screw.

1 shows in enlarged schematic partial view left and top of a screw according to the invention 10 with a steeper cone section 12 and a flatter cone section 14 , as well as in parts the screw head 16 and the screw shaft 18 , as well as right and down to the right side hole edge 20 of the through hole 22 a component 24 , For example, a transmission housing, wherein the steeper cone section 12 the screw and the transition area 28 between bevel 30 and adjacent cylindrically extending hole edge 20 still have no contact.

Angles are always given herein in relation to the vertical, be it a parallel to the hole axis or to the screw axis, which is only schematically illustrated in FIG 1 drawn on the left edge. The hole diameter of the unfetched hole section is 8.6 mm, that is, the screw has a clearance of about 0.3 mm on both sides.

The chamfer angle is 45 °, the angle of the steeper cone section 12 is about 25 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is about 1.3 mm. The diameter of the steeper cone section is approximately 9.3 to 9.4 mm adjacent to the screw head, resulting in a "cover" of the hole on both sides or radially seen from (9.4 mm - 8.6 mm) / 2 = 0, 4 mm results.

The screw 10 should now be screwed into the mating thread, not shown, to make the screw. The others 2 . 3 and 4 show this in each further rotated.

2 is a representation according to 1 , taking the screw 10 the expected contact point has already approximated by the first screwing, but still no contact has occurred.

3 is a representation according to 1 and 2 where the screw 10 with its steeper cone section 12 the transition area 28 the chamfer 30 to the cylindrical part of the hole in a small deformation section 34 deformed, the screw head itself but still has no contact with its support surface.

4 is a representation according to 1 . 2 and 3 , wherein the screw head has now been tightened with its target torque, and the deformation section 34 has become even larger, and where the required tension between the screw head and its support surface (see dashed zone 36 top right) and the voltage between the component with the through hole and the second component to be connected with the mating thread is achieved. Because the cone section 12 is sufficiently smooth and also the area of the chamfer 11 is sufficiently smooth, and the deformation occurs only when the contact between the cone portion and chamfer surface with a sufficiently large pressure, the deformed surface according to the invention forms a sealing surface, which is technically the cause of the required sealing function. This can be done without the interposition of any kind of sealing ring. Nevertheless, a sealing ring, a washer, a snap ring or the like can be inserted between the screw head and the bearing surface without endangering the functioning of the principle according to the invention.

Further embodiments with respect to a steel screw M8 for screwing into a conventional aluminum alloy, as used in the above-mentioned housings in the automotive industry, with a radial clearance of 0.3 mm are as follows:

2)

The chamfer angle is 45 °, the angle of the steeper cone section 12 is about 30 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is about 1.3 mm. The diameter of the steeper cone section is approximately 9.3 to 9.4 mm adjacent to the screw head, resulting in a "cover" of the hole on both sides or radially seen from (9.4 mm - 8.6 mm) / 2 = 0, 4 mm results.

3)

The chamfer angle is 45 °, the angle of the steeper cone section 12 is about 33 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is about 1.3 mm. The diameter of the steeper cone portion is adjacent to the screw head about 9.3 to 9.4 mm, resulting in a "coverage" of the hole on both sides or radially seen from (9.4mm - 8.6mm) / 2 = 0.4mm.

4)

The chamfer angle is 45 °, the angle of the steeper cone section 12 is about 35 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is about 1.3 mm. The diameter of the steeper cone section is approximately 9.3 to 9.4 mm adjacent to the screw head, resulting in a "cover" of the hole on both sides or radially seen from (9.4 mm - 8.6 mm) / 2 = 0, 4 mm results.

5)

The chamfer angle is 45 °, the angle of the steeper cone section 12 is about 38 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is approximately 1.4 to 1.8 mm. The diameter of the steeper cone section is approximately 9.3 to 9.4 mm adjacent to the screw head, resulting in a "cover" of the hole on both sides or radially seen from (9.4 mm - 8.6 mm) / 2 = 0, 4 mm results.

6)

The chamfer angle is 45 °, the angle of the steeper cone section 12 is about 40 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is about 1.5 mm. The diameter of the steeper cone section is approximately 9.3 to 9.4 mm adjacent to the screw head, resulting in a "cover" of the hole on both sides or radially seen from (9.4 mm - 8.6 mm) / 2 = 0, 4 mm results.

7)

The chamfer angle is 45 °, the angle of the steeper cone section 12 is only about 10 °, that of the flatter cone section 14 about 45 °.

The length of the steeper cone section measured along the cone is about 1.3 mm. The diameter of the steeper cone section is approximately 9.3 to 9.4 mm adjacent to the screw head, resulting in a "cover" of the hole on both sides or radially seen from (9.4 mm - 8.6 mm) / 2 = 0, 4 mm results.

As from the examples related to the 1 to 4 can be seen, the screw can also be used with more radial play, as long as the overlap is provided by the steeper cone section. The perpendicular line of the hole edge would be further offset to the right. The deformation range would thus be further shifted upwards, but the sealing surface would continue to exist, and the screw head would come to its desired edition and could produce reproducible stress on the components, because according to the invention, the cone length of the steeper cone section is significantly shortened compared to the prior art ,

With less radial clearance of the material of the component displacing conical section 12 respectively. 14 correspondingly displace more material. This is then possibly first with the flatter cone section 14 and only in the further course of screwing in with the steeper cone section 12 , Here are the limits of the screw connection is reached when the screw head breaks off before the screw head itself generates the desired voltage.

The inventive quality consists inter alia in that the radial clearance, the overlap area of the steeper cone section 12 and whose cone angle are adapted so that the required tension between the head and its bearing surface can actually be generated without already taking away too much of the tightening torque (usually a nominal dimension) for the screw to deform the material and thus to produce the sealing surface becomes. This can be done in principle with a steeper cone section 12 reach, which is steep enough. The above examples give some hints, but they are not an exhaustive choice. The angle of the flatter cone section can also be varied. Preferably, it is greater by an angle difference of 10 ° to 30 ° than that of the steep cone angle and preferably not significantly larger than the angle of the chamfer.

The transition between steep and shallow cone sections can also be rounded. Also, the cone contour does not necessarily have to be linear, but may be curved to some extent as long as the inventive principle is adhered to, as described above.

If the described embodiments are to be transferred to other screw sizes, then the characteristic variables such as hole diameter, clearance, screw diameter, cone lengths, etc., can generally be adapted proportionally.

If a rounded chamfer is used, the inventive principle is also applicable. Decisive are then the angles of the chamfer surface in the expected contact area.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10314948 [0004]

Claims (5)

Threaded screw ( 10 ) containing a shaft ( 18 ), which is provided with a thread suitable for screwing into a mating thread, and a screw head ( 16 ), which is to be overlaid with a chamfer ( 30 ) provided hole ( 22 ), characterized in that the shaft ( 18 ) between screw head ( 16 ) and the thread, preferably directly to the screw head ( 16 ), a steeply extending cone section ( 12 ) and in relation to this flatter transition section ( 14 ) to the further cylindrically extending shaft. The threaded screw of claim 1, wherein the angle Alfa of the steeply tapered cone portion to the screw axis is in the range of 5 ° to (Beta minus 2 °), and Beta is the angle of the chamfer ( 30 ) to the hole axis is, with a cone length in the range of 1.0 mm to 2.0 mm, and a difference between hole diameter and screw diameter of about 0.6 mm, based on a screw size M8. A threaded screw according to the preceding claim, wherein the range for Alfa is from 25 ° to 40 °, more preferably from 30 ° to 38 °, and even more preferably from 32 ° to 36 °. Threaded screw according to one of the preceding claims, wherein an annular circumferential groove is provided between the screw head and the steep cone section. Method for producing a screw connection between at least two components, wherein the one component ( 24 ) a beveled (bevel ( 30 )) Through hole ( 22 ) for the screw shaft ( 18 ), and the through-hole (FIG. 22 ) with the screw head ( 16 ), characterized by the steps of: a) inserting a screw ( 10 ) according to claim 1 in the through hole ( 22 ), b) screwing the screw into the mating thread, wherein initially only one of the two cone sections, preferably the steeper (( 12 ) against the transitional area ( 28 ) of the chamfer ( 30 ) to the cylindrical hole section ( 20 ) is pressed, this is deformed thereby, whereby a sealing surface ( 34 ) between the cone section of the screw and transition area forms at the hole, c) further screwing the screw until the screw head ( 16 ) exerts a force on its bearing surface, which is large enough to prevent loosening of the screw by vibration, or thermally induced expansion and shrinkage movements, or, the predetermined voltage between the screw head and bearing surface is reached.

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